In general, an air valve is primarily used for restricting a gas from flowing into an air valve body. If a user wants to change the flow of the gas, the user simply needs to control an adjusting switch of the air valve. However, the gas may leak easily when the user turns the adjusting switch, due to a poor internal structure of the switch. As to the air valve switch used for controlling the flow of a dangerous gas such as petroleum gas, the issue of leakage becomes a safety concern.
To prevent the leakage of an air valve, manufacturers and designers generally adopt a complicated structure with many components for the prevention of leakage. For example, U.S. Pat. No. 5,349,984 discloses a check valve provided for preventing a leakage, and the check valve includes a spring and a valve component, such that an elastomeric apertured plug plugged into a position of the valve body for stopping a leak. In U.S. Pat. No. 4,681,132, a check valve with a preset cracking pressure is disclosed for preventing a leakage, and the check valve includes a valve element reciprocatally positioned within a valve body, and both of the valve body and the valve element including valve seats seal together when the valve element is urged forwardly within the valve body. A plug is positioned within the rear of the valve body to constantly urge the valve element forwardly, thereby defining a cracking pressure necessary to unseat the valve seats to allow the flow of fluid through the valve body.
Since the conventional design of valves usually comes with a complicated structure with many components, the maintenance, repair or replacement of components become difficult, if it is necessary to replace a component that is worn out after being used for a long time. Obviously, the structure of the conventional valve requires improvements.